Ammoxidation is a well-known process in which an ammoxidizable organic compound is converted into a cyano compound in the presence of an ammoxidation catalyst at elevated temperature with ammonia and oxygen. Ammoxidation achieved industrial significance e.g. for the production of acrylonitrile from propylene, benzonitrile from toluene, phthalonitrile and terephthalonitrile from ortho- and para-xylene, 3-cyanopyridine from 3-picoline as well as hydrogen cyanide from methane (Andrussoff method)--see Ullmann's Encyclopedia of Industrial Chemistry, Vol. A5, 5.sup.th ed. (1986), pp. 328-29, 333, 343 as well as Vol. A8, 5.sup.th ed. (1987), pp. 159-62.
Up to the present, ammoxidation has been carried out exclusively using gaseous ammonia as the source of ammonia. Numerous catalysts have proven to be suitable for ammoxidation, e.g., binary oxides based on Bi.sub.2 O.sub.3 --MoO.sub.3, V.sub.2 O.sub.5 --MoO.sub.3 and V.sub.2 O.sub.5 --Sb.sub.2 O.sub.5 for the production of organic nitriles. Refer, e.g., for the production of hydrogen cyanide by the ammoxidation of methanol or formaldehyde to EP-A 0,107,638 and EP-A 0,121,032, according to which oxides of molybdenum and iron or oxides of phosphorus and an element from the series Fe, Co, Ni, Zn, B and U are used as catalysts. Numerous catalysts for the ammoxidation of e.g. propylene can be found in EP-A 0,311,334. For the ammoxidation of methylpyridines and suitable catalysts therefor, reference can be made to U.S. Pat. Nos. 4,447,612 and 4,482,719. Ammoxidation is usually carried out at a temperature between 200 and 600.degree. C. The Andrussoff process constitutes an exception. In this process, methane is ammoxidized to hydrogen cyanide at over 1000.degree. C. using noble-metal catalysts (Pt-Rh lattices).
It is known from experiments conducted by Nozawa et. al., Mokuzai Gakkaishi, 27 (1), 49-53 (JP) (1981) (see Chem. Abstr. 94:105119) that hydrogen cyanide is formed in the pyrolysis of wood or cellulose treated with diammonium phosphate. As the temperature increases the amount formed increases and achieves a maximum of 10 ml HCN gas/g at 900.degree. C., corresponding to 12 mg HCN/g burned wood. In the presence of oxygen the development of HCN is only 2 to 4 ml/g at 500 to 600.degree. C. and the development of HCN is considerably reduced at a rise in temperature to 700.degree. C. in the presence of oxygen. Although hydrogen cyanide is formed in this pyrolysis and diammonium phosphate can be regarded as a source for ammonia, this is not an ammoxidation since no catalyst is present. In addition, the yield of hydrogen cyanide is so low that this method cannot be considered for the industrial production of hydrogen cyanide.
It is also known that ammonium salts of organic carboxylic acids can be dehydrated at elevated temperature, approximately 300.degree. C., with the formation of corresponding nitriles. According to CS patent 160,810 (see Chem. Abstr. 85:80171) ammonium oxalate can be converted into dicyanogen and ammonium formate can be converted into hydrogen cyanide, using the device described in this document at 300.degree. C. An ammonium salt is used in this conversion; however, this is not an ammoxidation but rather a simple dehydration.
Ammonium salts are occasionally used in the production of ammoxidation catalysts, e.g., ammonium metavanadate according to U.S. Pat. No. 4,447,612 and ammonium paramolybdate according to EP-A 0,107,638; however, the actual ammoxidation catalyst is free of ammonium salts since the production process comprises a tempering process at 500.degree. C. and above.